/*
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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/*
 *
 *
 *
 *
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent.atomic;

import java.util.function.LongUnaryOperator;
import java.util.function.LongBinaryOperator;
import sun.misc.Unsafe;

/**
 * A {@code long} array in which elements may be updated atomically.
 * See the {@link java.util.concurrent.atomic} package specification
 * for description of the properties of atomic variables.
 *
 * @author Doug Lea
 * @since 1.5
 */
public class AtomicLongArray implements java.io.Serializable {

  private static final long serialVersionUID = -2308431214976778248L;

  private static final Unsafe unsafe = Unsafe.getUnsafe();
  private static final int base = unsafe.arrayBaseOffset(long[].class);
  private static final int shift;
  private final long[] array;

  static {
    int scale = unsafe.arrayIndexScale(long[].class);
    if ((scale & (scale - 1)) != 0) {
      throw new Error("data type scale not a power of two");
    }
    shift = 31 - Integer.numberOfLeadingZeros(scale);
  }

  private long checkedByteOffset(int i) {
    if (i < 0 || i >= array.length) {
      throw new IndexOutOfBoundsException("index " + i);
    }

    return byteOffset(i);
  }

  private static long byteOffset(int i) {
    return ((long) i << shift) + base;
  }

  /**
   * Creates a new AtomicLongArray of the given length, with all
   * elements initially zero.
   *
   * @param length the length of the array
   */
  public AtomicLongArray(int length) {
    array = new long[length];
  }

  /**
   * Creates a new AtomicLongArray with the same length as, and
   * all elements copied from, the given array.
   *
   * @param array the array to copy elements from
   * @throws NullPointerException if array is null
   */
  public AtomicLongArray(long[] array) {
    // Visibility guaranteed by final field guarantees
    this.array = array.clone();
  }

  /**
   * Returns the length of the array.
   *
   * @return the length of the array
   */
  public final int length() {
    return array.length;
  }

  /**
   * Gets the current value at position {@code i}.
   *
   * @param i the index
   * @return the current value
   */
  public final long get(int i) {
    return getRaw(checkedByteOffset(i));
  }

  private long getRaw(long offset) {
    return unsafe.getLongVolatile(array, offset);
  }

  /**
   * Sets the element at position {@code i} to the given value.
   *
   * @param i the index
   * @param newValue the new value
   */
  public final void set(int i, long newValue) {
    unsafe.putLongVolatile(array, checkedByteOffset(i), newValue);
  }

  /**
   * Eventually sets the element at position {@code i} to the given value.
   *
   * @param i the index
   * @param newValue the new value
   * @since 1.6
   */
  public final void lazySet(int i, long newValue) {
    unsafe.putOrderedLong(array, checkedByteOffset(i), newValue);
  }

  /**
   * Atomically sets the element at position {@code i} to the given value
   * and returns the old value.
   *
   * @param i the index
   * @param newValue the new value
   * @return the previous value
   */
  public final long getAndSet(int i, long newValue) {
    return unsafe.getAndSetLong(array, checkedByteOffset(i), newValue);
  }

  /**
   * Atomically sets the element at position {@code i} to the given
   * updated value if the current value {@code ==} the expected value.
   *
   * @param i the index
   * @param expect the expected value
   * @param update the new value
   * @return {@code true} if successful. False return indicates that the actual value was not equal
   * to the expected value.
   */
  public final boolean compareAndSet(int i, long expect, long update) {
    return compareAndSetRaw(checkedByteOffset(i), expect, update);
  }

  private boolean compareAndSetRaw(long offset, long expect, long update) {
    return unsafe.compareAndSwapLong(array, offset, expect, update);
  }

  /**
   * Atomically sets the element at position {@code i} to the given
   * updated value if the current value {@code ==} the expected value.
   *
   * <p><a href="package-summary.html#weakCompareAndSet">May fail
   * spuriously and does not provide ordering guarantees</a>, so is
   * only rarely an appropriate alternative to {@code compareAndSet}.
   *
   * @param i the index
   * @param expect the expected value
   * @param update the new value
   * @return {@code true} if successful
   */
  public final boolean weakCompareAndSet(int i, long expect, long update) {
    return compareAndSet(i, expect, update);
  }

  /**
   * Atomically increments by one the element at index {@code i}.
   *
   * @param i the index
   * @return the previous value
   */
  public final long getAndIncrement(int i) {
    return getAndAdd(i, 1);
  }

  /**
   * Atomically decrements by one the element at index {@code i}.
   *
   * @param i the index
   * @return the previous value
   */
  public final long getAndDecrement(int i) {
    return getAndAdd(i, -1);
  }

  /**
   * Atomically adds the given value to the element at index {@code i}.
   *
   * @param i the index
   * @param delta the value to add
   * @return the previous value
   */
  public final long getAndAdd(int i, long delta) {
    return unsafe.getAndAddLong(array, checkedByteOffset(i), delta);
  }

  /**
   * Atomically increments by one the element at index {@code i}.
   *
   * @param i the index
   * @return the updated value
   */
  public final long incrementAndGet(int i) {
    return getAndAdd(i, 1) + 1;
  }

  /**
   * Atomically decrements by one the element at index {@code i}.
   *
   * @param i the index
   * @return the updated value
   */
  public final long decrementAndGet(int i) {
    return getAndAdd(i, -1) - 1;
  }

  /**
   * Atomically adds the given value to the element at index {@code i}.
   *
   * @param i the index
   * @param delta the value to add
   * @return the updated value
   */
  public long addAndGet(int i, long delta) {
    return getAndAdd(i, delta) + delta;
  }

  /**
   * Atomically updates the element at index {@code i} with the results
   * of applying the given function, returning the previous value. The
   * function should be side-effect-free, since it may be re-applied
   * when attempted updates fail due to contention among threads.
   *
   * @param i the index
   * @param updateFunction a side-effect-free function
   * @return the previous value
   * @since 1.8
   */
  public final long getAndUpdate(int i, LongUnaryOperator updateFunction) {
    long offset = checkedByteOffset(i);
    long prev, next;
    do {
      prev = getRaw(offset);
      next = updateFunction.applyAsLong(prev);
    } while (!compareAndSetRaw(offset, prev, next));
    return prev;
  }

  /**
   * Atomically updates the element at index {@code i} with the results
   * of applying the given function, returning the updated value. The
   * function should be side-effect-free, since it may be re-applied
   * when attempted updates fail due to contention among threads.
   *
   * @param i the index
   * @param updateFunction a side-effect-free function
   * @return the updated value
   * @since 1.8
   */
  public final long updateAndGet(int i, LongUnaryOperator updateFunction) {
    long offset = checkedByteOffset(i);
    long prev, next;
    do {
      prev = getRaw(offset);
      next = updateFunction.applyAsLong(prev);
    } while (!compareAndSetRaw(offset, prev, next));
    return next;
  }

  /**
   * Atomically updates the element at index {@code i} with the
   * results of applying the given function to the current and
   * given values, returning the previous value. The function should
   * be side-effect-free, since it may be re-applied when attempted
   * updates fail due to contention among threads.  The function is
   * applied with the current value at index {@code i} as its first
   * argument, and the given update as the second argument.
   *
   * @param i the index
   * @param x the update value
   * @param accumulatorFunction a side-effect-free function of two arguments
   * @return the previous value
   * @since 1.8
   */
  public final long getAndAccumulate(int i, long x,
      LongBinaryOperator accumulatorFunction) {
    long offset = checkedByteOffset(i);
    long prev, next;
    do {
      prev = getRaw(offset);
      next = accumulatorFunction.applyAsLong(prev, x);
    } while (!compareAndSetRaw(offset, prev, next));
    return prev;
  }

  /**
   * Atomically updates the element at index {@code i} with the
   * results of applying the given function to the current and
   * given values, returning the updated value. The function should
   * be side-effect-free, since it may be re-applied when attempted
   * updates fail due to contention among threads.  The function is
   * applied with the current value at index {@code i} as its first
   * argument, and the given update as the second argument.
   *
   * @param i the index
   * @param x the update value
   * @param accumulatorFunction a side-effect-free function of two arguments
   * @return the updated value
   * @since 1.8
   */
  public final long accumulateAndGet(int i, long x,
      LongBinaryOperator accumulatorFunction) {
    long offset = checkedByteOffset(i);
    long prev, next;
    do {
      prev = getRaw(offset);
      next = accumulatorFunction.applyAsLong(prev, x);
    } while (!compareAndSetRaw(offset, prev, next));
    return next;
  }

  /**
   * Returns the String representation of the current values of array.
   *
   * @return the String representation of the current values of array
   */
  public String toString() {
    int iMax = array.length - 1;
    if (iMax == -1) {
      return "[]";
    }

    StringBuilder b = new StringBuilder();
    b.append('[');
    for (int i = 0; ; i++) {
      b.append(getRaw(byteOffset(i)));
      if (i == iMax) {
        return b.append(']').toString();
      }
      b.append(',').append(' ');
    }
  }

}
